The speaker says that “those who ne’er succeed” place the highest value on success. (They “count” it “sweetest”.) To understand the value of a nectar, the speaker says, one must feel “sorest need.” She says that the members of the victorious army (“the purple Host / Who took the flag today”) are not able to define victory as well as the defeated, dying man who hears from a distance the music of the victors.
The three stanzas of this poem take the form of iambic trimeter—with the exception of the first two lines of the second stanza, which add a fourth stress at the end of the line. (Virtually all of Dickinson’s poems are written in an iambic meter that fluctuates fluidly between three and four stresses.) As in most of Dickinson’s poems, the stanzas here rhyme according to an ABCB scheme, so that the second and fourth lines in each stanza constitute the stanza’s only rhyme.
Many of Emily Dickinson’s most famous lyrics take the form of homilies, or short moral sayings, which appear quite simple but that actually describe complicated moral and psychological truths. “Success is counted sweetest” is such a poem; its first two lines express its homiletic point, that “Success is counted sweetest / By those who ne’er succeed” (or, more generally, that people tend to desire things more acutely when they do not have them). The subsequent lines then develop that axiomatic truth by offering a pair of images that exemplify it: the nectar—a symbol of triumph, luxury, “success”—can best be comprehended by someone who “needs” it; the defeated, dying man understands victory more clearly than the victorious army does. The poem exhibits Dickinson’s keen awareness of the complicated truths of human desire (in a later poem on a similar theme, she wrote that “Hunger—was a way / Of Persons outside Windows— / The Entering—takes away—”), and it shows the beginnings of her terse, compacted style, whereby complicated meanings are compressed into extremely short phrases (e.g., “On whose forbidden ear”).